Detecting phase transitions in a CaCl-HO system at low temperatures using a fiber-optic Fresnel reflection sensor.

Temperature-induced crystallization events in an aqueous calcium chloride solution in the concentration range of 15-40 mass% are monitored using an optical fiber Fresnel reflection sensor in the temperature range of 30°C to -200°C. The deviation of the phase boundary from equilibrium and the formation of an eutectic mixture followed by its densification during rapid cooling are inferred from the distinct signatures of the optical fiber sensor via the changes in refractive index. During the natural heating at laboratory ambient conditions, the optical signals impart the completion of dissolution of ice and CaCl·6HO.

Monitoring phase changes in supercooled aqueous solutions using an optical fiber Fresnel reflection sensor.

We report on a technique for monitoring the crystallization of water and aqueous solution of NaCl at atmospheric pressure, when cooled via liquid nitrogen, using a Fresnel reflection-based optical fiber sensor. The crystallization of distilled water and the associated changes in refractive index inferred from the sensor response comply with the previous reports on physical properties of supercooled water. The phase separation of NaCl.